A Tainted Smile

(Y/N) Koizumi, the student council President of the famous night school program. A year ago, she went to England for unknown reasons and now she's back. Everyone looks up to her like she's the perfect role model but her fake smiles could fool anyone. The mystery is, who is she? How does she know that Yui is the sacrificial bride of the Sakamaki's? Will that smiling mask of hers fool the vampires? Or her mask would break and show her what she truly is.